Re: Sailboat performance change
Vertical dodger windows rarely 'look' right.. and you need to be a little careful with dodger height - another 'visual' that needs to be the best compromise between utility and appearance. Because we had a large, high bridge deck we spent a lot of time mocking up ideas until we came up with what would work and not look silly. A large radius dodger frame is one way (as opposed to 'hard shouldered' square-ish frames) to get more ability to 'look around' it and a higher center 'look through' area.
As to modifying the main I'd be tempted to leave the tack alone and just have the clew raised as much as you need, minimizing the loss of sail area and simplifying the modifications. That may involve relocating the vang connection if it's a rigid vang, but otherwise it's just a sail recut rather than moving the gooseneck.
1984 Fast/Nicholson 345 "FastForward"
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)